Garmin nuvi 300 asking for pin number
Unfortunately, even if you perform master reset on Garmin GPS unit, it does not reset Garmin Lock security feature, which password-protect most Garmin electronic devices to deter theft. If you forget the PIN or password unlock code to unlock the Garmin unit, the best solution is to bring it to Garmin to get unlocked. “Secure Location” does not unlock a locked Garmin unit either as it’s only a temporary fix as when it’s turn on outside the security location, the device is locked again."
So unfortunately, there is only one option: You have to send your nüvi into the Garmin, who can unlock it. Remember original receipt.